Schematic illustration of the experimental design. Approximately 500 two week old adult T. castaneum beetles (population SB or Cro1) were reared under standardized conditions (30°C, 60% relative humidity, 12/12 h light/dark cycle). After 24 h of egg-laying, eggs were separated from beetles and further incubated. Hatched larvae were then individualized into 96’-well plates and assigned to either oral or pricking challenge with B. thuringiensis. Naïve controls from oral and pricking infection were pooled upon RNA isolation. For RNA isolation, 32 larvae were pooled for one replicate per treatment. In total, three replicates for each treatment were used which results in a total number of 1,536 animals that were used for this study (32 larvae × 4 treatments × 2 populations × 2 time points × 3 replicates).